The present invention generally relates to communications systems and, more particularly, to wireless systems, e.g., terrestrial broadcast, cellular, Wireless-Fidelity (Wi-Fi), satellite, etc.
Recently, Cognitive Radio (CR) (e.g., see, J. Mitola III, “Cognitive Radio: An Integrated Agent Architecture for Software Defined Radio,” Ph.D. Thesis, Royal Institute of Technology, Sweden, May 2000) has been proposed to implement negotiated, or opportunistic, spectrum sharing to provide a viable solution to the problem of sparsity of the wireless spectrum. To operate CR properly, it is important to perform spectrum sensing, i.e., the ability to detect licensed signals in their assigned spectrum bands. As a result, spectrum sensing becomes one of the core technologies of CR. The most challenging part of performing spectrum sensing is sensing signals in very low signal-to-noise ratio (SNR) conditions.
In this regard, a Wireless Regional Area Network (WRAN) system is being studied in the IEEE 802.22 standard group. The WRAN system is intended to make use of unused television (TV) broadcast channels in the TV spectrum, on a non-interfering basis, to address, as a primary objective, rural and remote areas and low population density underserved markets with performance levels similar to those of broadband access technologies serving urban and suburban areas. In addition, the WRAN system may also be able to scale to serve denser population areas where spectrum is available. Since one goal of the WRAN system is not to interfere with TV broadcasts, a critical procedure is to robustly and accurately sense the licensed TV signals that exist in the area served by the WRAN (the WRAN area). For instance, for sensing the presence of an ATSC DTV (Advanced Television Systems Committee Digital Television) broadcast signal, the miss detection probability should not exceed 0.1 subject to a 0.1 probability of false alarm when the SNR is −20.8 dB.